We investigated using commercially available CaptureSelect CH1-XL affinity resin from Thermo Fisher Scientific for purification of bispecific antibody CD3-TAA. A purification matrix based on the ZCa protein A–derived domain displays calcium-dependent binding of IgG and elution under mild conditions ( 10). An alternative approach makes use of novel ligands for affinity capture. For example, 2 M arginine at pH 4.3 has been used to elute human human immunoglobulin G (IgG) 1 from protein A under relatively mild conditions ( 9). Most studies have focused on moderating the pH needed for elution. Methods to reduce the risk of aggregation during protein A chromatography have been discussed elsewhere. Second, the low-pH condition required for elution from protein A potentially causes aggregation of both active and inactive BsAb product variants ( 8). Teneobio faced two potential issues when considering protein A as the method of capture: First, all variants containing intact Fc domains (BsAb CD3-TAA, CD3 homodimer, and TAA homodimer) would copurify. Although used for bulk capture and high-resolution binding of antibody products, the method can be challenging with bispecific antibodies because of the multiplicity of structures. The common method for purifying monoclonal antibodies (MAbs) and BsAbs following harvest and clarification uses affinity capture with a commercially available protein A resin. The predominant active form is a heterodimer (BsAb CD3-TAA) however, numerous inactive forms consisting of CD3 and TAA homodimers, half-antibodies, and excess light chains can contaminate expressed product. Figure 1 illustrates the variants of bispecific antibody CD3-TAA–expressed products. It brings an inherent potential to form inactive product variants that copurify with active products. The main challenge of producing bispecific antibodies comes with their heterogenous nature. The number of bispecific antibodies in clinical testing is growing rapidly ( 7), and so is the need for efficient production and purification strategies. It relies on noncovalent interactions, the result of complementary mutations in the CH3 domains ( 5) and hinge-region disulfide bonds, to form heterodimers ( 6). Correct pairing of heavy chains is achieved through knobs-into-holes technology. The human kappa light chain is bound to the full-length heavy chain.
#Capto mmc impres full
One heavy chain is full length (OmniFlic derived) and the other - discovered in UniRat transgenic rats ( 4) - is truncated, lacking the CH1 domain. The lead molecules are composed of three chains: two nonidentical human heavy chains and a human kappa light chain. Using proprietary UniRat human heavy-chain technology combined with OmniFlic human fixed–light-chain antibody technology licensed from Ligand Pharmaceuticals, Teneobio has produced several bispecific antibodies, each targeting a different tumor antigen and CD3 ( 3). Such BsAbs mediate cell killing by binding simultaneously to an antigen that is overexpressed on tumor cells and to the CD3 receptor, activating cytotoxic T lymphocytes ( 2). Note that only the full-length anti-CD3 human heavy chain has a CH1 domain, and the anti-CD3 human heavy chain is present in only two forms: the CD3-TAA heterodimer and CD3 homodimer.īispecific antibodies (BsAbs) are designed to recognize and bind two different antigens, in many cases for the purpose of immune effector-cell activation to destroy cancer cells ( 1). Aggregated forms of product also are present. Other forms include the TAA homodimer, CD3 homodimer, half-antibody, and L chain, all of which are inactive. Figure 1: Variant forms of BsAb CD3-TAA–expressed products the CD3-TAA heterodimer (containing one light (L) and two heavy (H) chains) is the active form.
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